In pattern transfer applications, the etch step contributes to resolution and line width control because of the thickness and uniformity of the residual layer. The residual layer thickness is a based on conservation of volume and depends on the starting thickness, and the duty cycle and height of the imprint feature.

Residual layer variation is a function of pattern density simply caused by material not being able to redistribute. Can be minimized by long fill times, in practice people use short fill time and deal with the variation. Post imprint planarization processes such as SFIL-R can reduce the line width variation. Drop dispense systems can simple change the volume of material depending on the local pattern duty cycle. MII have reported using a automated program to analyze pattern data files and change the material dispense appropriately.

All the results above were for hard templates, soft PDMS templates tend to distort during imprint. A three layer mold with a 4 x harder organo-silicon top surface has shown 50 nm resolution at close to 1 atmosphere (Plachetka 2005).

CYCLE TIMEThe cycle times have been improving significantly over the last few year. Depends on many factors including materials pressure and pattern type. Some typical data that has been reported includes;

• < 0.1 random defects per squ cm > 250 nm, and 12 fixed defects per squ cm maintained for 12 wafers, 30 fields per wafer. The fixed defect count was achieved on the third mold that had been fabricated, the defect density had dropped 100 x over the 3 cycles of learning. Reported by MII using drop dispense and a proprietary release strategy (Shumaker 2005)

Also, depends critically on the overall facility and process cleanliness.